The present invention relates to a differential transimpedance amplifier.
A transimpedance amplifier refers to an amplifier which receives a current and outputs a voltage signal. The transimpedance amplifier is used for a high-speed communication receiving stage such as an optical receiver for 100 Gbps Ethernet, an optical link, or a board to board interconnection, etc. Korea Patent Publication No. 2010-0138057, which was filed by an applicant of the present invention, exists as a conventional art related to the transimpedance amplifier.
A conventional transimpedance amplifier has a single-ended configuration, and is a structure of obtaining one output from one input signal. Accordingly, when the transimpedance amplifier is used for a receiving stage in which noise sensitivity is important, an influence of power noise and ground noise is great.
In order to reduce the influence of the noise, since a low pass filter should be implemented when adding a single-ended to a differential-ended conversion circuit, a die size is increased. A replica circuit can be used for the single-ended to differential-ended conversion circuit, but the die size and power consumption is still increased.
In order to solve the problems of the conventional art described above, the present invention is directed to a differential transimpedance amplifier capable of obtaining a differential output corresponding to an input signal without increasing a die size and power consumption compared with a conventional art.
Further, the present invention is directed to a differential transimpedance amplifier capable of controlling an input resistance of a circuit by controlling a feedback resistance.
An aspect of the present invention provides a differential transimpedance amplifier, including: a common gate amplifier configured to receive an electrical signal from an input node; and a common source amplifier configured to have a feedback resistor and receive the electrical signal from the input node, wherein an output signal of the common gate amplifier and an output signal of the common source amplifier form a differential signal pair.
According to an embodiment of the present invention, since each output signal of a common gate amplifier and a common source amplifier forms a differential signal, a differential pair may be implemented without forming a passive low-pass filter or a replica circuit for single-ended to differential-ended conversion and thus a die size and power consumption may be decreased.
Further, since an input resistance of the common gate amplifier and a gain of the common source amplifier are controlled by controlling a feedback resistance, a symmetric differential output may be obtained.